Nature of enamel

Enamel is obtained from a mixtirre of raw materials mineral and/or frits. The raw materials used are mainly feldspars, kaolirt, quartz and chalk or dolomite. Frits are close mixtures of components prepared by melting several compounds at high temperature (T 1,400°C). After quenching in air or water, the product, markedly 

It is customary to classify the various types of enamel, based on the nature of the flux used. Thus, we can distinguish lead enamels (PbO rich enamels), boron oxide enamels, alkaline enamels, alkaline-earth enamels, zinc enamels and bismuth oxide enamels [STE 85]. Lead enamels, historically the oldest, were the most commonly used for a long time. Because of the toxicity of lead, their future hinges on the evolution of legislation relating to the leaching of this element. They terrd to be replaced by enamels containing a very small qrrantity of bismuth oxide ( 5% mass) and, especially by alkaline borosilicate products. 

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